Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Hassium, symbol Hs, chemical element with atomic number 108. It is produced artificially by nuclear fusion (in which an element with larger atoms is produced by fusing together smaller atoms from other elements). Each hassium atom has a very large nucleus, or central mass, containing positively charged particles called protons and neutral particles called neutrons. The large number of particles in the nucleus makes the atom unstable and causes the atom to split apart into smaller components soon after it is created. In 1997 the International Union of Pure and Applied Chemistry named element 108 hassium (Hs), which was previously called unniloctium, to honor the Heavy-Ion Research Laboratory in Darmstadt, Germany. Researchers at this laboratory discovered elements 107, 108, 109, 111, and 112. The name hassium is derived from the German state Hassia, which is where the research was performed.

Hassium has the atomic number 108, which means that each Hs atom contains 108 protons in the nucleus. Scientists have created several isotopes of hassium, or different forms of the element that contain different numbers of neutrons in the nucleus. For example, hassium-263 contains 108 protons and 155 neutrons (108 protons + 155 neutrons = atomic mass 263). Similarly, bohrium-265 contains 108 protons and 157 neutrons.

Hassium was first created in 1984 by nuclear fusion of the smaller elements lead (Pb) and iron (Fe). Because the hassium nucleus contains so many particles, the atom is unstable and undergoes spontaneous fission, a process in which the atom breaks into smaller “daughter” components. When the atom splits, it releases energy in the form of electromagnetic waves and electrically charged bits of matter. This energy is known as radiation (see Radioactivity).

Scientists at the Heavy-Ion Research Laboratory discovered hassium-265, an isotope with a lifespan of only 0.0036 seconds. The most stable isotope of element 108 is hassium-263, which has a lifespan of 2 seconds. By 1998 four isotopes of hassium were confirmed: 263, 264, 265, and 267.

Hassium belongs to Group 8 (VIIIb) on the periodic table, which also contains the naturally occurring elements iron (Fe), ruthenium (Ru), and osmium (Os). Iron, ruthenium, and osmium are all shiny, silvery metallic solids with melting points above 1500° C (2732° F). These elements form stable oxides (compounds containing oxygen). Because elements in the same group, or column, on the periodic table often share similar properties, scientists expect hassium to share properties with other Group 8 elements. However, because of the limited amount of hassium that can be produced and its short lifespan, scientists have been unable to determine chemical properties of this unstable element.